氧离子导体La2Mo2-xMxO9(M=Cr,W)的理论研究

采用第一性原理方法研究了高温β-La₂Mo₂O₉中Mo被Cr或W取代后晶体的结构性质和高温相稳定性.研究发现Cr和W分别倾向于占据具有4配位数和5配位数的Mo位.W取代体系晶胞参数相对取代浓度非线性变化.该非线性变化与W离子取代位置配位数降低以及体系内La—O和Mo(W)—O平均键长非线性变化有关.内聚能计算表明W取代Mo后能够有效稳定高温相结构,降低相变温度.La₄Mo₃W₁关键词： 氧离子导体 第一性原理 晶体结构 相稳定性

Theorectical study of the oxide-ion conductor

We perform the first-principles study of the structural properties and the high temperature phase stabilization of Cr, W-doped β-La₂Mo₂O₉. We find that Cr prefers the site with four coordination numbers and W atom preferentially occupies the site with five coordination numbers. The nonlinear dependence of cell parameter on W content in W-doped systems results from the nonlinear change in Mo(W)-O and La-O bond lengths with W content and the decrease of coordination number around W occupied site. The decrease of cohesive energy with the W-doped concentration is conducive to the understanding of the stabilization of the β-La₂Mo_2-xW_xO₉ at lower temperature. The appearance of stronger W-O bond leads to the increase of the energy barrier of oxygen-ion concerted motion in W-dopedβ-La₂Mo₂O₉.